This invention pertains to a supervision control system for supervising the inflow of cells to an ATM switching system.
The ATM switching system switches cells having fifty-four (54) bytes split from various data, such as voice data, image data and other numerical data, and transmits in a multiplexed form the various data at different transmission speed. Of the fifty-four (54) bytes in a cell, forty-eight (48) bytes form an information field and six (6) bytes form a header part. Of the four (4) bytes, i.e. thirty-two (32) bits, in the header part excluding two (2) bytes forming a tag, twenty-eight (28) bits indicate a VPI/VCI (virtual path identifier/virtual channel identifier), two (2) bits indicate a PT (payload type), one (1) indicates a CLP (cell loss priority) and one (1) bit is for a RES (reserve).
A buffer in a multiplexer for these cells can experience an overflow when an unexpected number of cells flow in. Since overflowing cells are discarded, the communications quality is deteriorated. Although such a problem can be avoided by using a buffer having a larger capacity, a larger delay results, which is critical in transmitting voice data, image data, and so forth.
Therefore, a buffer is required in which the occurrence of an overflow and its effect are minimized.